1. Field of the Invention
The present invention generally relates to a retaining seal member used for, for example, an exhaust gas cleaning apparatus, and an exhaust gas cleaning apparatus including a retaining seal member.
2. Description of the Related Art
For the past century and continuing, the number of automobiles is dramatically rising. In proportion to this rise, the amount of exhaust gas released from internal combustion engines of the automobiles is rapidly increasing. Since various substances contained in the exhaust gas (particularly, exhaust gas of diesel engines) lead to air pollution and the like, the exhaust gas containing such substances has a serious effect on the global environment.
Under such circumstances, various exhaust gas cleaning apparatuses have been proposed and put to actual use. A typical exhaust gas cleaning apparatus has a casing (metal shell) disposed at the midstream of an exhaust pipe that is connected to an exhaust gas manifold of the engine. The casing (metal shell) has a configuration in which an exhaust gas processing member having numerous fine-sized pores is provided therein. One example of the exhaust gas processing member is an exhaust gas cleaning filter including, for example, a catalyst carrier or a Diesel Particulate Filter (DPF). For example, in a case of the DPF, the above-described configuration allows fine particles contained in the exhaust gas passing through the exhaust gas processing member to be caught by the walls surrounding the fine-sized pores. Thereby, the fine particles can be removed from the exhaust gas. The material used for forming the exhaust gas processing member includes, for example, a metal material, an alloy material, and a ceramic material. One example of an exhaust gas processing member formed of a ceramic material is a Cordierite honeycomb filter. From the aspects of, for example, thermal resistance, mechanical strength, and chemical stability, a porous silicon carbide has been recently employed as the material used for forming the exhaust gas processing member.
The exhaust gas processing member and the metal shell have a retaining seal member (typically having a cylindrical shape) interposed therebetween. The retaining seal member prevents the exhaust gas processing member from being damaged by abutting the metal shell, for example, in a situation where the automobile is running. Furthermore, the retaining seal member also prevents exhaust gas from leaking from the space between the metal shell and the exhaust gas processing member. Furthermore, the retaining seal member serves to prevent the exhaust gas processing member from being detached by the exhaust pressure of the exhaust gas. Moreover, the exhaust gas processing member is desired to have a heat insulating property for retaining a high temperature, so that reactivity can be maintained. One example of a retaining seal member that satisfies these conditions is a sheet material formed of an inorganic fiber such as an alumina fiber.
The sheet material is wrapped around an outer peripheral surface of the exhaust gas processing member except for the surface of its opening and is fixed to the exhaust gas processing member to form a united body. Thereby, the sheet material provides the functions of the exhaust gas processing member. Then, this united component is installed in the metal shell, to thereby form a part of the exhaust gas cleaning apparatus.
One method of installing the united body in the metal shell is performed by dividing the metal shell into two semi-circle shaped parts, disposing the united body into the metal shell, and joining the two semi-circle shaped parts together to form a cylindrical shaped metal shell. Another method of installing the united body in the metal shell is performed by providing C-letter shape or U-letter shape cross-section parts in the metal shell, disposing the united body into the metal shell, and closing up the cross-section parts to form a cylindrical shaped metal shell. From the aspect of improving workability and simplifying manufacturing steps, another further method of installing the united body in the metal shell is performed by preparing a cylindrical shaped metal shell and assembling the metal shell and the united body together by pressing the united body into the metal shell.
In a conventional method of forming the retaining seal member and the exhaust gas process member into a united body by wrapping the retaining seal member around the exhaust gas process member, a sheet material 124 having the dimensions for wrapping around the exhaust gas process member is prepared and is cut into a shape having two mutually engaging end parts, in which one is a protruding part and the other is a notch part (See FIG. 1). Accordingly, the retaining seal member is fixed to the outer periphery part of the exhaust gas process member by wrapping the sheet material 124 around the outer periphery of the exhaust gas process member, fitting the protruding part into the notch part, and taping together the end parts (for example, see Japanese Laid-Open Patent Application No. 2002-68709).